...fog is between the eye and the top of the building than there is from the eye to its base. The parallel tower seen at a long distance in fog will show itself the thinner the nearer it is to its base. This arises from the preceding [proposition], which says: Fog shows itself the whiter and denser the nearer it is to the ground; and by the 2nd of this, which says: A dark thing will appear of so much smaller figure the more it is seen against a background of powerful whiteness. Therefore, the fog being whiter at the base than at the top, it is necessary that the darkness of such a tower show itself narrower at the base than at the top.

[464] On cities or other buildings seen in the evening or morning in fog [at long distance]. Book B, folio 3. Buildings seen at a long distance, in the evening or morning, in fog or thick air, show only the brightness of their parts illuminated by the sun, which lies toward the horizon; and the parts of the said buildings which are not seen by the sun remain almost of the colour of the mediocre darkness of the fog.

[465] Why the higher things placed at a distance are darker than the lower ones, even though the fog be uniform in thickness. Book B, folio 3. Of things placed in fog, or other thick air, or through vapour, or smoke, or through distance, that one will be the more notable the higher it is; and of things of equal height, that one will appear darker which is set against...